A Modulation and Demodulation Module for Underwater Acoustic Communication of Combined Frequency Signals

Abstract

The invention discloses an underwater acoustic communication modulation and demodulation module for combined frequency signals, which belongs to the technical field of underwater communication and electronics. The invention uses an embedded processor to control a special combined-frequency signal and single-frequency signal codec chip CMX865A for wired communication, as a hardware modem for underwater acoustic signals. The signal transmission part adopts the combined frequency or single frequency baseband signal generated by CMX865A and the local oscillator carrier of the processor to mix and modulate the frequency. After frequency selection and power amplification by the switched capacitor filter, the transducer is driven to realize the modulation and transmission of the encoded signal. The underwater acoustic signal input by the receiving circuit is pre-amplified by the gain control chip, the frequency selection of the switched capacitor filter, the switching frequency mixing, and the low-pass filtering. The recovered baseband signal is demodulated by the CMX865A hardware and sent to the processor. The modulation and demodulation process is completed by a special chip, so that the whole circuit has low power consumption, high speed, simple structure and strong anti-interference ability.

Description

technical field [0001] The invention belongs to the technical field of underwater acoustic communication and underwater acoustic electronics, and relates to a modulation and demodulation module for underwater acoustic communication of combined frequency signals. Background technique [0002] Underwater acoustic communication technology was originally used for military and national defense. With people's attention to the development of underwater resources such as oceans and lakes, the demand for information transmission technology related to various civil underwater aquaculture, underwater detection and underwater robots has soared. . Underwater communication mainly uses underwater sound as the information carrier, and the technical threshold is relatively high. In order to reduce the application cost and be accepted by the civilian market, it is necessary to continuously develop new underwater communication technology products. [0003] At present, the main methods of unde...

AI Technical Summary

Problems solved by technology

This method uses single-frequency transmission, which has a low utilization rate for the channel. At the same time, the demodulation device needs to perform frequency discrimination and judgment on the transmitted signal, so the transmission speed is slow and the interference is large.

[0005] 2. Amplitude keying (ASK): ASK is the opposite of FSK. It multiplies the binary code with a single frequency signal and transmits information through the change of signal amplitude. This method requires high signal quality and is resistant to intersymbol interference and multiple It is suitable for fixed-point and fixed-distance communication, and the transmission rate is roughly the same as that of FSK, and the transmission rate has not been improved.

[0006] To sum up, at present, single-frequency mode is mostly used for underwater data transmission, and software demodulation is often used, which requires strong computing power and high power consumption.

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